Conventional scanners process packages by reading and decoding information affixed to the packages. In some instances, the information is read and decoded as the packages move along a conveyor system. Typically, the scanners incorporate a light source and a light-detecting means, such as charge-coupled device (CCD) sensors, complementary metal-oxide-semiconductor (CMOS) sensors, or avalanched photodiode (APD) sensors. A portion of the light that is reflected from the package is detected by the sensors and converted into an electrical signal, which is the basis for the object properties that include digital images of a package that has been read by the scanner. The reflected light is processed and decoded according to the instructions executed by one or more computer processors of the conventional scanners or the conveyor system.
The conventional scanners may be manufactured with two or more lasers. The two or more lasers may be focused at different distances inside a single scanner. The multiple foci may increase the depth of field for reading of images (e.g., barcodes) affixed to the packages. In the conventional scanners, the lasers related to the various focuses are activated sequentially and alternately: one for each scanning operation. If one scan is found to contain the image, all subsequent scans are performed by the same laser, until the object is outside of the depth of field for the scanner. After scanning of the image is complete, scanning may resume with cyclic alternation of the lasers.
In other conventional systems, the depth of field of the scanner may be increased by employing a laser with an adjustable lens. As the position of the lens changes, the focal point of the laser beam in relation to the laser scanner may increase or decrease.
These two conventional systems have drawbacks that include slow processing times, low scan rates, and increased points of failure due to moving mechanical parts. The moving focus mechanism of the scanner is relatively slow, expensive, and can be a potential reliability problem. To overcome these and other drawbacks, an improved scanner system that employs advanced digital signal processing with better reliability is provided below.